The present invention relates to improvements of a manipulator head.
The present invention has been developed with particular regard to a manipulator device for pieces of sheet metal of the type forming the subject of the following applications, all of which are based on Italian Patent Application Nos. 67703-A/89 and 67704-A/89 both filed on Aug. 16, 1989.
Japanese Patent Application No. 2-216462
U.S. patent application Ser. No. 07/567,727, now U.S. Pat. No. 5,176,022.
U.K. Patent application No. 9017741.1
German Patent Application No. P4025988.9
French Patent Application No. 9010392
Korean Patent Application No. 90-12769
Swedish Patent Application No. 9002675-8
Chinese Patent Application No. 79108086
Swiss Patent Application No. 2656/90
Austrian Patent Application No. A 1698/90
FIGS. 1 and 2 schematically show a part of these applications. In FIGS. 1 and 2, two motor-driven manipulator heads indicated 2 and 4 are provided with respective attachment members 6, 8 rotatable on the heads 2, 4 about respective axes A, A'. In FIG. 1, respective gripping tools 10, 12 are fixed to the attachment members 6, 8 for gripping a metal sheet 1. In a different configuration of use, the attachment members 6, 8 are connected to operating equipment 16.
As a result of working tolerances, the axes of rotation A, A' of the heads 2, 4 may not be exactly coincident. In FIGS. 1 and 2, the error in the alignment of the axes has been exaggerated in order to facilitate understanding of the problem. Observation of FIGS. 1 and 2 makes it clear that the error in alignment of the axes A, A' causes considerable problems in the taking up of the sheet 1 or the equipment 16. This error causes further problems when the two attachment members are to contribute equally to the transmission of driving torque to the equipment 16.
Obviously, the problem of the relative errors in the geometry of the manipulator heads also exists in the more general case of a manipulator device having a single head to which any operating tool is connected.
The present invention further relates to an attachment device of the type comprising a base body connected to a manipulator head and having associated means for generating a force for retaining the tool, in which the body and the tool have constraining means for establishing the exact position of the tool relative to the head. The constraining means include a pair of cooperating abutment surfaces on the body and on the tool which are kept in contact as a result of the force exerted by the generating means and are adapted to establish the position of the tool relative to the head along a first line of constraint.
The above-mentioned applications describe a device for gripping metal sheet in which the interchangeable tool is constituted by a plate for picking up metal sheets and having a seat in which a base body carried by the head of a manipulator device is inserted. The force which retains the plate is generated by permanent magnets carried by the base body. The position of the plate relative to the body is defined by the contact between the walls of the cavity of the plate and corresponding walls of the body. The working tolerances of the contact surfaces of the body and the plate must be particularly close so that the plate is connected to the head without any play. The close tolerances between the contact surfaces, however, mean that the plate must be located in an extremely precisely defined position and the movement of the manipulator head towards the plate must also be extremely precise in order for the plate to be engaged without sticking or interference.